Electrocution - Workplace Safety and Health Council

PREFACE
This compilation of case studies on fatalities in the construction industry
is initiated by the Workplace Safety and Health Council, and put together
by the WSH Construction Committee in collaboration with the Ministry
of Manpower. This booklet depicts how the accidents occurred and
provides valuable learning points on how they may have been prevented.
This is the first in a series of such booklets to be published.
As much as the next few years promise to be exciting for the construction
industry, they also pose a great challenge to the industry to maintain
workplace safety and health. Construction sites have customarily been
viewed as high-risk workplaces, which more often than not have a higher
incidence of workplace fatalities. We must address this perception and
change the reality. While construction workers strive to complete a building
or facility, it is important that they do not risk life and limb. It is crucial
that these workers go home safely after work each day.
This booklet of case studies offers insights to all in the industry on how
these tragic accidents occurred, so that we may glean important, lifesaving
lessons from the experience. In learning from our past mistakes,
we can and must prevent these mishaps from happening again. Together
with your help, we can transform construction sites into safe and healthy
workplaces for our workers.
Mr Lee Tzu Yang
Chairman
Workplace Safety and Health Council

Struck by Falling Objects
Case 1 Pinned by a brick wall 64
Case 2 Pinned by a collapsed roof slab 67
Case 3 Struck by falling beams 70
Case 4 Struck by steel beams 73
Case 5 Struck by falling material in a trench 76
Case 6 Struck by a crane boom 78
Case 7 Hit by a collapsed wall 81
Case 8 Hit by steel rebars 84
Case 9 Buried under collapsed soil 87
Case 10 Crushed by a collapsing boom 90
Case 11 Struck by falling timber 92
Case 12 Struck by a falling crane boom 95
Case 13 Struck by a collapsed wall 97
Electrocution
Case 1 Electrocution by a faulty residual circuit breaker 100
Case 2 Killed by an exposed electrode holder 103
Struck By or Against Objects / Machines
Case 1 Hit by a scissors lift platform 108
Case 2 Hit by a moving vehicle 111
Case 3 Hit by a moving crane 114

ELECTROCUTION

CASE 1
ELECTROCUTION BY A FAULTY RESIDUAL
CIRCUIT BREAKER
Description of Accident
Deceased was assigned to plaster
the ceiling of the ground floor at
the loading/unloading bay of a
factory under construction. A
boom lift was used to enable him
to reach the ceiling for plastering.
He was found lying on the ground
at the loading/unloading bay.
Autopsy reported deceased died
of electrocution.
1. Deceased was found lying here
2. Trench
Causes and Contributing
Factors
• A pail of mixed cement and
a cement mixing tool were
found at the scene. A portable
extension socket outlet that
was connected to the main
switch board was also found
at the scene.
• Even though insulation tests
performed on the cement mixing
tool, extension socket outlet and
main switch board were
satisfactory, the autopsy revealed
that the cause of death was
consistent with electrocution.
1. Extension socket outlet
2. A pail containing mixed cement
3. Trench
4. Deceased was found lying here
5. Cement mixing tool
100 Electrocution

• A residual circuit breaker (RCCB)
installed at the main switch
board was found to be defective.
Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Contact with electricity
• Defective tools, equipment or materials
• Inadequate maintenance
• Maintenance regime
Follow-up
The occupier was instructed to implement the following
improvements/measures at the worksite:
• Electrical tools, appliances and circuit breakers installed on the
main switch boards are to be inspected by a qualified electrician
monthly to ensure that they are in good working condition.
• All generator sets are to be inspected by a Licensed Electrical
Worker before use.
Electrocution
101

Recommendations
Implement the use of Socket Outlet Assembly (SOA).
Ensure all electrical tools, appliances and circuit breakers (including
RCCB) installed on the main switch boards are inspected by a
qualified electrician periodically to ascertain the working condition.
Enforce the use of personal protective equipment.
102 Electrocution

CASE 2
KILLED BY AN EXPOSED ELECTRODE HOLDER
Description of Accident
A worker was carrying out welding
work in a factory premises to
erect a mezzanine floor.
He was found dead on the metal
structure of the mezzanine floor
that was being erected. He was
holding a welding electrode
holder in his right hand and it
was resting on his chest.
The autopsy reported that the
worker died of electrocution.
Causes and Contributing
Factors
1.The deceased was found lying here
2. The C channels
3. The horizontal I-beam
4. The isolator
5. Welding cable
6. The AC welding set
• A metal jaw and part of the metal
upper handle of the electrode
holder was exposed as the plastic
insulation covering had
broken off.
• The worker was probably
electrocuted when his body
came into contact with the
energised exposed metal part
of the electrode holder.
1. Part of the insulation covering for the
upper handle of the electrode holder
had broken off, exposing the metal part
2. The metal jaw of the electrode holder
was exposed
3. Welding electrode
Electrocution
103

Root Cause Analysis
Evaluation of loss
Type of contact
Immediate cause(s)
Basic cause(s)
Failure of SMS
• One worker killed
• Contact with electricity
• Defective tools and equipment
• Inadequate maintenance
• Maintenance regime
Follow-up
A Stop Work Order was issued.
The company was instructed to implement the following safety
measures:
• All AC arc welding sets to be fitted with low voltage
shock preventors.
• All electrode holders, welding cables, cable connectors to be
inspected before use.
• No welding work to be carried out in wet conditions.
104 Electrocution

Recommendations
Fit all AC arc welding sets with low voltage shock preventors.
Inspect all electrode holders, welding cables and cable connectors
before use.
Conduct regular maintenance of all equipment.
Ensure overall supervision of welding work.
Electrocution
105

Published in June 2008 by the
Workplace Safety and Health
Council in collaboration with
the Ministry of Manpower.
All rights reserved. This
publication may not be
reproduced or transmitted in
any form or by any means,
in whole or in part, without prior
written permission. The
information provided in this
publication is accurate as at time
of printing. All cases shared in this
publication are meant for learning
purposes only. The learning points
for each case are not exhaustive
and should not be taken to
encapsulate all the responsibilities
and obligations of the user of this
publication under the law. The
Workplace Safety and Health
Council does not accept any
liability or responsibility to any
party for losses or damage arising
from following this publication.